A set of imidazolium-based ionic liquids (ILs), 1-(2-hydroxyethyl)-3-methylimidazolium chloride (1), 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2), and 1-butyl-2,3,4,5-tetramethylimidazolium bromide (3), has been synthesized and their structural and thermal behavior studied. Organic halides are well-known IL formers with imidazolium halides being the most prominent ones. Functionalization of the imidazolium cation by enhancing its hydrogen bonding capacity, i.e. through introduction of -OH groups or by diminishing it, i.e. through substitution of the ring hydrogen atoms by methyl groups is expected to change the inter-ionic interactions. Consequently, the solid-state structures of 1-3 have been characterized with means of single X-ray diffraction to shed light on preferential inter-ionic interactions for obtaining valuable information on anti-crystal engineering, i.e. designing ion combinations that favor a low melting point and exhibit a low tendency for crystallization. The study reveals that endowing IL forming ions with an enhanced hydrogen bonding capacity leads to a depression in melting points and kinetically hinders crystallization. This study provides hints towards new design concepts for IL design, similar to the common strategy of employing conformationally flexible ions.